In the present study, stage- and age-specific predatory patterns and nutritional ecology attributes of four co-occurring aphidophagous ladybirds, namely, Coccinella septempunctata (L.), Coccinella transversalis F., Cheilomenes sexmaculata (F.) and Propylea dissecta (Mulsant) on pea aphid, Acyrthosiphon pisum (Harris) were investigated. Despite their lower consumption rates, smaller ladybirds (C. sexmaculata and P. dissecta) and earlier instars were efficient converters of aphid prey with higher relative growth rates, over the respective larger ladybirds (C. septempunctata and C. transversalis) and fourth instars. The consumption rates of pea aphids by the larvae increased with stage, but with a decline in the later part of the fourth instars, just prior to pupation. Adult females of early age groups (between 2 and 7 days) had higher consumption rates than later age groups in all the four species. Further in adult females, consumption rates decrease with increase in age, but without significant changes in conversion efficiencies and relative growth rates.

In the present study, the predatory interactions between two locally abundant large lady beetles, Coccinella septempunctata L. (C7) and Coccinella transversalis F. (Ct) provided with either an extremely scarce, scarce, sub-optimal, optimal or abundant supply of the pea aphid, Acyrthosiphon pisum (Harris) were investigated. For this, three 2-predator combinations (conspecific C7 + C7 and Ct + Ct, and heterospecific C7 + Ct) of 10-day-old unmated adult females were used. The relationships between the proportion of prey consumed by the predators in the conspecific and heterospecific combinations when provided with five different abundances of prey were similar in consisting of a decelerating (type II) functional response when provided with an extremely scarce to optimal supply of prey, followed by an accelerating (type III) functional response when provided with an optimal to abundant supply of prey. It is likely that the modified type II functional response recorded in the present study was a consequence of using a small experimental arena (Petri dish). The multiplicative risk model analysis revealed that the predators interacted antagonistically except in the C7 + C7 combination provided with an extremely scarce supply of prey where the predators had an additive effect. The predators in the heterospecific C7 + Ct combination consumed fewer aphids when provided with an extremely scarce, scarce, sub-optimal or optimal supply of prey prey than the predators in conspecific C7 + C7 combination but a similarly high number when provided with an abundant supply of prey. In addition, the efficiency of converting prey biomass into their own biomass was higher in the heterospecific C7 + Ct than in the conspecific C7 + C7 or Ct + Ct combinations at all prey densities. Although the conversion efficiency of the predators in the conspecific and heterospecific combinations provided with an extremely scarce supply of prey was the highest recorded, their growth rate was the lowest. In contrast, both the conversion efficiency and growth rate of the predators in the three combinations were highest when provided with an abundant supply of prey. It may, therefore, be concluded that when the predators in the combinations occupy similar ecological niches, they will probably consume less prey than they require when prey is both scarce and abundant because the predators interact antagonistically.

Parthenium hysterophorus L. (Asteraceae) is an alien herbaceous weed with a pantropical distribution. The weed adversely affects grazing land productivity, native biodiversity and causes respiratory and dermal allergies in humans. The weed continues to invade new countries, with increases in CO₂ set to further enhance this spread. Biological control is among the most cost-effective management strategy for P. hysterophorus, with the leaf-feeding beetle Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) among the most promising candidates. Our review discusses the life cycle and feeding and reproductive behaviours of Z. bicolorata. We emphasise how abiotic factors and biological processes, viz. ageing, rhythmicity, multiple matings and interactions amongst species, influence the fertility and mortality parameters of the beetle. We anticipate that this review will assist in improving the strategies for rapid mass-multiplication of Z. bicolorata in laboratories. In addition, the review will support efforts to develop classical biological control approaches in regions where Parthenium is invasive.

The nutritive quality of aphids, conspecific and heterospecific eggs as food for ladybirds is a controversial issue. If ladybirds find aphids more palatable than eggs then they are more likely to efficiently exploit and be biocontrol agents of aphids. If eggs of conspecific or heterospecific ladybirds are more palatable than aphids these biocontrol agents may either impede aphid pest suppression or become a threat to other species of ladybirds. Thus, prior to formulating predatory guilds of ladybirds the nutritive quality of their eggs compared to that of the target aphid needs to be determined. In this regards, the present study evaluates the nutritive quality of an ad libitum supply of: (i) pea aphid, Acyrthosiphon pisum (Harris), (ii) conspecific eggs and (iii) heterospecific eggs as food for Coccinella septempunctata (L.) and Coccinella transversalis Fabricius (Coleoptera: Coccinellidae), by determining the stage specific predation and developmental attributes of these two ladybirds reared on these diets. The conversion efficiencies and growth rates of young (first, second and third) larvae of both species of ladybirds were higher than those of fourth instar larvae and the consumption rates of fourth instar were higher than those of young larvae when fed on the three diets. When fed aphids the pre-imaginal development was faster, the consumption rates, conversion efficiencies and growth rates higher, adults bigger and mortality lower than when fed on conspecific eggs. The larvae of C. septempunctata consumed and completed their development when fed eggs of C. transversalis but the first instar larvae of C. transversalis did not consume the eggs of C. septempunctata and died of starvation. The dominance of C. septempunctata over C. transversalis in agricultural fields may be due to it consuming and utilizing aphids more efficiently and as a consequence growing faster and suffering a lower mortality along with its ability to consume and complete its development on eggs of C. transversalis. Thus, both these predators may not continue to coexist as predators of the pea aphid in agricultural fields since C. septempunctata may become a greater threat to C. transversalis in the future.

The potential of four co-occurring ladybirds, Coccinella septempunctata (L.), Coccinella transversalis (F.), Cheilomenes sexmaculata (F.), and Propylea dissecta (Mulsant), as predators of the pea aphid, Acyrthosiphon pisum (Harris) was investigated. Larger ladybirds were more voracious while smaller ones had higher consumption indices and were more efficient converters of food.